User blog comment:Davidhater/On Devil triggers, Devil modes and Devil forms/@comment-6769189-20190417213503/@comment-39037298-20190418104203

As I pointed out in OP, DT in japanese referres to gauge (double DT = 2 gauges), while shin majin referres to appearance. It's only natural that because of how this mode was activated in 2 most players didn't use it, so he decided to improve that same concept.